(1) Field of the Invention
The present invention relates to a process for producing a sintered aluminum alloy. More particularly, the sintered aluminum alloy prepared according to the present invention is characterized in that it has properties of small weight, high strength and excellent wear resistance. Accordingly, it is suitable for use in the production of machine parts such as gearwheels, pulleys, compressor vanes, connecting rods, pistons and so forth.
(2) Description of Prior Art
In view of the economy in energy consumption and the improvement in mechanical efficiency, the trend to use light-weight machine parts is growing. In comparison with ordinary cast alloys, it is possible for the sintered aluminum alloy to make a high-Si alloy containing fine crystals of pro-eutectic Si, so that the sintered aluminum alloy is expected as a material having excellent specific strength and wear resistance.
Such sintered aluminum alloys are disclosed in Japanese Laid-Open Patent Publication Nos. H4-365832, H7-197168, and H7-197167 and U.S. Pat. No. 5,545,487. Any of these alloys contains a certain amount of Si and is improved in strength and wear resistance having a dapple grain structure. The dapple grain structure herein referred to has specific areal ratios of Al-solid solution phase and Al—Si alloy phase, in the latter of which pro-eutectic Si crystals of a certain particle size are dispersed.
Although the above-mentioned sintered aluminum alloys have high strength and high wear resistance, however, in recent years, the alloys having higher strength and smaller thickness are demanded. Furthermore, because the above-mentioned alloys have deviations of strengths, cast machine parts must be made thick to a certain extent. Still further, there is room for improvement in the elongation property and the fatigue strength of the sintered aluminum alloys, so that the sintered aluminum alloy is expected to be improved further.